Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2023 Apr;25(4):67-75.
doi: 10.1007/s11908-023-00798-5. Epub 2023 Mar 7.

Lactobacillus iners and genital health: molecular clues to an enigmatic vaginal species

Johanna B Holm  1   2 , Kayla A Carter  1 , Jacques Ravel  1   2 , Rebecca M Brotman  1   3
Affiliations

Lactobacillus iners and genital health: molecular clues to an enigmatic vaginal species

Johanna B Holm et al. Curr Infect Dis Rep. 2023 Apr.

Abstract

Purpose of review: Vaginal lactobacilli are recognized as important drivers of genital health including protection against bacterial vaginosis and sexually transmitted infections. Lactobacillus iners is distinct from L. crispatus, L. gasseri, and L. jensenii by its high global prevalence in vaginal microbiomes, relatively small genome, production of only L-lactic acid, and inconsistent associations with genital health outcomes. In this review, we summarize our current understanding of the role of L. iners in the vaginal microbiome, highlight the importance of strain-level consideration for this species, and explain that while marker gene-based characterization of the composition of the vaginal microbiota does not capture strain-level resolution, whole metagenome sequencing can aid in expanding our understanding of this species in genital health.

Recent findings: L. iners exists in the vaginal microbiome as a unique combination of strains. The functional repertoires of these strain combinations are likely wide and contribute to the survival of this species in a variety of vaginal microenvironments. In published studies to date, strain-specific effects are aggregated and may yield imprecise estimates of risk associated with this species.

Summary: The worldwide high prevalence of Lactobacillus iners warrants more research into its functional roles in the vaginal microbiome and how it may directly impact susceptibility to infections. By incorporating strain-level resolution into future research endeavors, we may begin to appreciate L. iners more thoroughly and identify novel therapeutic targets for a variety of genital health challenges.

Keywords: Lactobacillus iners; bacterial vaginosis; metagenome; sexually transmitted infections; transcriptome; vaginal microbiome.

PubMed Disclaimer

Conflict of interest statement

Conflict of Interest JR is co-founder of LUCA Biologics, a biotechnology company focusing on translating microbiome research into live biotherapeutics drugs for women’s health. Dr. Holm reports personal fees from Intralytix Inc., outside the submitted work. All other authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Gram stains of L. iners cultured isolates highlight variable cell morphology and Gram staining within (arrows) and between strains.
Fig. 2
Fig. 2
Single nucleotide variants (SNV) in Lactobacillus iners 16S rRNA genes (indicated with “v”) are not specific to a genomically-distinct L. iners strain. (“-“ indicates spaces in the alignment). Strain names indicated by colored font.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Petrova MI, Reid G, Vaneechoutte M et al. Lactobacillus iners: Friend or Foe? Trends Microbiol. 2017;25(3):182–191. 10.1016/j.tim.2016.11.007 - DOI - PubMed
    1. Vaneechoutte M Lactobacillus iners, the unusual suspect. Res Microbiol. 2017;168(9–10):826–836. 10.1016/j.resmic.2017.09.003 - DOI - PubMed
    1. Zheng N, Guo R, Wang J et al. Contribution of Lactobacillus iners to Vaginal Health and Diseases: A Systematic Review. Front Cell Infect Microbiol. 2021;11(792787. 10.3389/fcimb.2021.792787 - DOI - PMC - PubMed
    1. Carter KA, Fischer MD, Petrova MI et al. Epidemiologic evidence on the role of Lactobacillus iners in sexually transmitted infections and bacterial vaginosis: a series of systematic reviews and meta-analyses. Sexually Transmitted Diseases. - PMC - PubMed
    1. Cohen CR, Lingappa JR, Baeten JM et al. Bacterial vaginosis associated with increased risk of female-to-male HIV-1 transmission: a prospective cohort analysis among African couples. PLoS Med. 2012;9(6):e1001251. 10.1371/journal.pmed.1001251 - DOI - PMC - PubMed